“…We focused on children's equal sign interpretation because it is widely regarded as important for success in algebra (e.g., Alibali, Knuth, Hattikudur, McNeil, & Stephens, 2007;Booth & Davenport, 2013;Carpenter, Franke, & Levi, 2003;McNeil & Alibali, 2005a, b). The equal sign (=) is a relational symbol, indicating that the two sides of an equation are equal and interchangeable (Kieran, 1981); however, children tend to view the equal sign operationally, meaning "add up the numbers" or "the answer" (Baroody & Ginsburg, 1983;Behr, Erlwanger, & Nichols, 1980;De Corte & Verschaffel, 1981;Kieran, 1981;Matthews & Rittle-Johnson, 2009;McNeil & Alibali, 2005a;Oksuz, 2007;Perry, 1991;Sáenz-Ludlow & Walgamuth, 1998).…”